Method and apparatus for laser-assisted hair transplantation

ABSTRACT

A laser treatment method and apparatus is provided which facilitates the grafting of hairs on the skin of a living human. The methodology involves a carefully designed treatment protocol utilizing a modified optical apparatus. The apparatus is a modified erbium-based laser system, designed for optimal therapeutic selectivity.

CLAIM TO BENEFIT OF EARLIER FILING DATE

This application is a divisional application of Ser. No. 08/820,761filed on Mar. 19, 1997. The contents of the aforementioned applicationare hereby incorporated by reference.

This application claims the benefit of the prior filed co-pendingprovisional application Ser. No. 60/014418, filed on Mar. 29, 1996 for"Use of the Er:YAG laser for hair transplantation".

FIELD OF THE INVENTION

The present invention is directed to the practice of skin ablation andin particular to the transplantation of micrografts and minigrafts ofhair on the skin utilizing a modified high power erbium laser systemunder carefully controlled conditions.

BACKGROUND

Over 1000 practitioners undertake hair transplantation in the UnitedStates, principally utilizing conventional techniques.

Under a conventional approach a scalpel or trephine punch is used tograft and implant circular or rectangular hair bearing areas. Typically,hair bearing areas from the rear of the scalp containing one or severalhair follicles are removed and transplanted to the alopecic (bald) site.

These hair bearing tissue samples are then manually positioned inrecipient sites consisting of previously prepared craters or incisionsin the tissue. Such historical surgical approaches have utilized roundand slit shaped recipient site preparation. Round recipient sites areprepared with circular punches, while slit-shaped recipient sites areprepared with surgical scalpels. Round grafts have been favored forhigher graft density, while slit grafts present a more natural profile.Hair may be transplanted as micrografts containing 1-2 hairs or asminigrafts containing 4-5 hairs. The typical recipient site will beprepared to a tissue depth of approximately 3 mm.

Several disadvantages attend conventional hair transplantationtechniques. Round grafts can appear `clumpy` and unnatural, while slitgrafts can compress the transplanted hair, creating a raised, unnaturalappearance, especially with darker, coarser hair. This is a consequenceof the fact that the scalpel is not removing a section of alopecicscalp, but rather creating a gaping slit, of typical length 5-6 mm.Further, the compression may be associated with hypoxia and hair growthfailure.

It has been suggested (Unger, W. P., Joum. Derm. Surg. Oncol., 20, 8,1994) that the precise removal of a section of alopecic scalp tissuewould eliminate any compression, while simultaneously presenting thepotential for a higher density of transplanted hair, since alopecicscalp would actually be removed. These factors, together with thepotential reduction of operative bleeding, led to the initiation oftrials in 1992 of laser induced slit transplant preparation using midinfra-red CO₂ lasers emitting at 10.6 μm. Such laser assisted hairtransplantation has been reported using carbon dioxide lasers insuperpulsed or scanned mode. Under such techniques, hair bearing sitesare removed and prepared as before, while the laser is used to preparethe recipient site.

In the first reported study (Unger, W. P., Joum. Derm. Surg. Oncol., 20,8, 1994), Unger described treatment of a limited number of patientsusing a superpulsed CO₂ laser, with up to 450 mJ applied at 12-15 Wattaverage power along a line 0.2 mm wide by 3 mm long. Here, the laser wastraced along a series of such interweaving lines, which immediately gapeto 0.5 mm, with superficial de-epithelialization and proximal tissuedamage. Crater depth was not reported.

While the pulsed CO₂ laser was capable of hemostatic injury, Unger foundit useful to increase the applied fluence to create some minimalbleeding, to better retain the transplanted hairs. Bleeding isindicative of the good vascular supply necessary to ensure graft take.In the absence of such, Unger noticed a significant failure rate.Results were acceptable at high fluence levels, although regrowth ofhair was delayed by some 2-6 weeks when compared with scalpel slits,probably due to proximal tissue necrosis.

Continuous wave CO₂ lasers have also been used for hair transplantation.Grevelink has described (Grevelink, J. M., Obj. Tech. Oto. Head NeckSurg, 5, 4, 1994) the use of a Sharplan 15 Watt laser with scanner tocreate a recipient site of diameter 2 mm and depth up to 6 mm. A singlepatient was so treated, with minimal operative bleeding. A wide zone ofcoagulative necrosis of width 175 μm was created around the crater.Follow up data has not been published and graft viability is unknown.

The wide zone of hemostasis associated with use of the CO₂ laser is aconsequence of the non-optimal choice of wavelength. At the CO₂ laserwavelength of 10.6 μm, tissue absorbs most of the energy within 50 μmalthough a wider tissue volume can be affected. This results in widertissue injury and hemostasis than would be optimal. It is likely thatthe hemostasis associated with the use of the CO₂ lasers described abovewill also impair graft take viability, since such hemostasis isassociated with a coagulative damage zone around the recipient site. Theprotracted erythematous period as noted is indicative of the cellularrepair and angiogenic processes associated with significant woundformation. As a consequence of this wound formation, transplanted hairfollicles may not receive sufficient nourishment during or subsequent tothis healing phase.

This document describes a method and apparatus for skin ablation and forthe reduction of the adverse effects associated with laser hairtransplantation.

SUMMARY OF THE INVENTION

The present invention comprises a laser treatment method and apparatusfor preparing recipient sites for implanting hair bearing tissue on thescalp.

The treatment method, according to one embodiment of the invention,includes:

irradiating a selected treatment site of alopecic scalp tissue with apulsed coherent light having a wavelength substantially in the range of2.5-3.5 μm, the light having an energy fluence substantially in therange of 1-200 J/cm², a pulsewidth substantially in the range of100-2000 microseconds, and a spot area incident on the treatment sitesubstantially in the range of 10⁻³ to 10⁻¹ cm²,

controlling exposure duration at the treatment site of the light toproduce with the irradiation a controlled ablation depth of 1-5 mm atthe treatment site,

directing the light to produce a plurality of recipient sites in saidalopecic scalp tissue, whereby slit-shaped recipient sites are producedwhich are suitable for receiving transplanted grafts, wherein each ofthe slit-shaped sites is angled in a direction corresponding to a localprevalent direction of hair growth, and

further directing the light to produce the recipient sites in anirregular grid pattern wherein the slit-shaped sites have adjacentpositions which are linearly offset.

The effect of producing the slit-shaped recipient sites corresponding tothe local prevalent direction of hair growth is illustrated in FIG. 1which shows an alopecic scalp section (1), locally resident hairs withintheir germinative follicle (2), and a laser ablated recipient site (3).

The treatment method is further characterized by:

A regime of pre-medication to modify tissue healing response andminimize incidence of adverse effects.

Controlling hemostasis, as by using intra-dermal epinephrine containing(˜1:200 000) anesthesia.

Allowing the skin to heal for a period of 2-16 weeks.

One apparatus for practicing the foregoing embodiment consists of amodified high power erbium laser system producing round orelliptical-shaped spots. This apparatus is further characterized by theavailability of an angled stand-off to facilitate a non-orthogonalincidence of laser exposure. Such an angled exposure more closelyapproximates the direction of local hair growth, the apparatus is alsoprovided with a port by which positive pressure flow of an inert gas canbe introduced, thereby maintaining the integrity of local optics. Anadjacent port may be used to introduce water flow to create a fineaerosol spray.

The invention incorporates a modified laser apparatus with newapplication, together with a novel treatment method for the ablation oftissue and for the preparation of viable sites for hair transplantation.The new treatment method thus developed presents the potential fornumerous significant advantages, particularly relating to precision ofablation and to minimization of proximal site damage and precise removal(ablation) of alopecic scalp tissue. By comparison, the CO₂ laser has amuch reduced absorption in tissue (by a factor of 10) and is less suitedto precise ablation and fashioning of recipient sites. Creation of awell defined transplant site with minimal proximal damage in turnimproves the prospect of viability of the grafted hair bearing tissue.This development of a clinically effective therapeutic treatment using acarefully controlled modified laser apparatus with associatedminimization of adverse effects is a major improvement and advance overcurrent options.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference may be had to the following detailed description and theaccompanying drawing, in which:

FIG. 1 is a representation of a recipient site including slits forreceiving graft transplants formed from a non-orthogonal incident oflaser exposure in the practice of the invention where each of the slitsare angled in a direction corresponding to a local prevalent directionof hair growth;

FIG. 2 is a graph illustrating absorption depth in water as a functionof illuminating wave length;

FIG. 3 shows a therapeutic treatment device having laser head cabinetrycontaining a laser source, an articulated arm or fiber delivery system,a handpiece containing focusing lenses, an angled standoff distancegauge, a gas port for introducing positive pressure flow of inert gasand an adjacent irrigation port for introducing water flow, according toan embodiment of the invention;

FIG. 4 shows a distal beam delivery device having an articulateddelivery system and a small diameter water flow tube terminating in afine nozzle. according to an embodiment of the invention; and

FIG. 5 shows adjacent recipient sites linearly offset over the area ofan alopecic scalp, according to the practice of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Theoretical Considerations:

When selection of laser type is under consideration, the two mostsignificant variables to consider are wavelength and pulsewidth.Wavelength defines depth of penetration of the light. As shown in FIG.2, the wavelength of the erbium laser, around 2.9 μm, exhibits thehighest degree of absorption in water, which is the principalconstituent of skin tissue. Collagen, another significant constituent ofskin tissue, also exhibits high absorption near 2.9 μm, with its localabsorption peak at 3.03 μm. Use of a wavelength close to the 2.9 μmabsorption peak of water leads to an efficient ablative process. Bycomparison, the CO₂ laser, with a tenfold diminished absorptioncoefficient, is a poor dermal ablation tool. The erbium laser has alsobeen used to ablate hard dental tissue, which has a much lower watercontent in the range 2-13%.

Selection of pulsewidth is of equal importance. When hair transplantsite preparation is underway, it is critical that the resultant heatproduction is unable to conduct widely into the surrounding dermis andthereby compromise follicular viability. This dictates that the appliedpulse duration of the energy be well matched to the mechanicalcharacteristics of the absorbing tissue volume. The concept of `thermalrelaxation time` has been introduced to describe the time period withinwhich a target tissue area loses half of its heat. In the instance of ahair transplant site preparation, it is important that the energy beapplied in a time period of less than 1 millisecond, well within thethermal relaxation time interval of the targeted tissue segment.

In accordance with the above criteria, a method has been developed inwhich a modified erbium laser, with optical beam delivery, focusingapparatus, and gas/fluid ports, is employed to prepare a host site forthe transplantation of hair bearing tissue.

It is instructive to first review the superficial ablation of tissueusing infrared lasers as described by previous researchers. Such workhas centered on the study of the ablation of superficial lesions such aspigmented marks and benign tumors.

The application of superficial tissue ablation has been studiedextensively by Professors Kaufmann and Hibst since 1989, who havepublished a number of papers (Kaufmann, R., Hartmann, A., Hibst, R., J.Dermat. Surg. Oncol. 1994, 20, 112-118.; Kaufmann, R., Hibst, R. 1990,Clin. Exp. Derm.; Hibst, R., Kaufmann, R. 1990, Las.Med.Sc., 6, 391-7.)Further work has been reported by Walsh (Walsh, A. J., and Cummings, C.,1994, Las. Surg. Med., 15(3), 295-305.).

In this section, results are compared and interpreted and open issuesassociated with the published literature are identified. This provides auseful background to the development of the new treatment method andapparatus to the application of more precise dermatological tissueremoval and to the field of hair transplantation.

In early studies by Kaufmann, Hibst and Walsh, a relatively low powererbium laser was employed. This laser was capable of a pulse energy of300 mJ, with maximum repetition rate of 5 Hz and fixed pulse width of250 μsec. More recently, more powerful variants have been employed.

Kaufmann and Hibst have studied a number of different models, includinganimals, both in-vitro and in-vivo, and a limited number of in-vivohuman patients presenting with epidermal and dermal lesions and tattoos.

In one of the above papers, the authors considered the application ofmultiple pulses at 1 Hz and 2 Hz on excised and in-vivo samples of pigskin. A 2 mm thickness of excised tissue was exposed with pulses ofvariable fluence at each of the two repetition rates. These measurementswere used to plot induced crater depth per pulse as a function offluence, for fluence levels up to 80 J/cm². These results indicated thatan in-vitro skin thickness of up to 400 μm could be removed by a singlepulse with a high fluence of up to 80J/cm².The results further indicatedthat higher repetition rates might compromise the ablation achieved perpulse, since maximum per pulse ablation was found to be reduced toapproximately 320 μm at 2 Hz. The in-vivo portion of this studydemonstrated minimal coagulation around the resultant crater, ofmagnitude less than 200 μm in all cases. Further, width of damage zonedid not correlate with applied energy density (it should be noted herethat later work by Walsh did find a slight correlation between fluenceand damage zone width). The authors concluded that the use of highradiant exposures increases ablation rate without an accompanyingdeleterious increase in proximal damage.

Absent from some of this work is a detailed correlation between in-vitroand in-vivo ablation rates. The impact of any bleeding during ablationis thus neglected and the likely precise compromise in ablation rateunidentified. Also absent from this early work is an extension of theablation measurements to the 5 Hz repetition rate available with thelaser used. It was therefore not clear if the trend in reduced ablationper pulse would continue as repetition rate increased to 5 Hz or beyond.The issue would be further complicated in the in-vivo situation by therate at which blood flows into the crater. These issues are inadequatelyaddressed in the published literature.

In all exposures reported in the earlier papers, the authors noted anabsence of hemostasis associated with the use of the Erbium laser,resulting from the narrow width of proximal coagulation (typicallyaround 50 μm in width). Further, concurrent saline cleaning was requiredto remove blood ingress. The impact of this process on total ablationtime was not presented. Rapid healing of the Erbium induced wounds wasnoted, similar to that found with scalpel incisions.Re-epithelialization occurred in less than 7 days. The effects ofcurrent generation higher repetition rates available on current systemsmight further introduce a measure of hemostasis not seen in earlyexperiments. Indeed, unpublished reports of hemostatic potential areemerging from several sources.

In a 1994 paper (Kaufmann, R., Hartmann, A., Hibst, R., J. Dennat. Surg.Oncol., 20, 112-118), the authors compare a number of IR lasers (Ho, Tm,Er, CO₂) as ablative tools on pig skin in vivo. Compared to the otherlasers studied, the Erbium laser was found to result in minimal woundhealing processes of granulation tissue formation and inflammatoryinfiltration, and to re-epithelialize more rapidly. Incidence of theseprocesses can be related to degree of trauma during the initial woundcreation process. Maximum repetition rate of the Erbium laser as used inthis study was 10 Hz. The authors noted that use of a fluence aroundthreshold, together with high repetition rate, resulted in tissuedesiccation and significant coagulation. This resulted from the completetransformation of all the laser energy to heat, in a cumulative fashion.At low repetition rates generally, a tedious ablation process resulted,although the authors noted that increased repetition and higher fluenceled to a more efficient process. At higher fluence (250 mJ in a 1 mmspot, equating to approximately 32 J/cm²), an ablation crater depth ofapproximately 40 μm was produced. The authors further speculated thatthe Erbium laser had the promise of versatility in degree of hemostasis,as repetition rate and fluence were increased.

When the reported work is reviewed as a whole, and thresholds andablation rates derived, several discrepancies emerge and it becomesapparent that a number of questions remain unanswered. Contradictionsare apparent in the published literature and the optimum method ofextension of the parameters previously applied is not addressed in thecontext of the deep tissue ablation requirement of the hairtransplantation application. Further, the previously publisheddermatological work basically addresses only the removal of superficiallesions, rather than the precise sculpting of crater shapes andorientations as would be required for the application of hair transplantsite preparation.

A wide variance in ablation rate was reported by these authors, from aslittle as 1 μm/J/cm² to as much as 5 μm/J/cm². The higher figure was anin-vitro ablation rate at low repetition, uncomplicated by the ingressof blood. In-vivo rates varied from 1-3 μm/J/cm² under single pulseconditions. Such single pulse conditions should obviate the impact ofblood ingress on the 250 μs time scale and greater comparability withthe bloodless in-vitro situation would be expected. No explanation ispresented for the deviation between in-vivo and in-vitro results,although the higher tensile stress under which the in-vivo samples weresituated would also explain part of the higher threshold and hence lowerablation rate. Limited evidence has also been presented that ablationrate per pulse has a repetition rate dependence, although thisdependence is not addressed in detail.

The in-vitro ablation rates correlate reasonably well with thosereported by Walsh (Walsh, A. J., and Cummings, C., 1994, Las. Surg.Med., 15(3), 295-305.). At high fluence in the range 20-60 J/cm², anablation rate of 1-3 μm/J/cm² was reported. At fluence levels in the60-80 J/cm² region, Walsh noted the induction of a limiting plasma,which defined maximum fluence. Walsh did note, however, an increase inwidth of thermal damage zone at higher fluence.

The present invention determines the appropriate minimum ablation rateper pulse which would result from the use of the higher energy morerepetitious Erbium lasers now available.

If a (minimum) ablation rate of 1 μm/J/cm² is assumed and a 1000 mJsystem operating at 15 Hz with 1 mm spot size is used (fluence of 127J/cm² per pulse), a theoretical minimum ablation rate of 120 μm perpulse can be predicted. A minimum cumulative ablation rate of up to 1.8mm/sec would then be expected from this extrapolation of clinical data.This would provide an adequate incision depth for site preparationwithin about 2 seconds. In practice, this parameter set could be used toquickly ablate a single circular recipient site, or several adjacentrecipient sites resulting in a longitudinal slit. The sites would then`gape` somewhat under the influence of local lines of tissue tension. Itis hence important that initial exposure site dimensions be less thanultimately required especially in the direction parallel to that oflocal lines of tissue tension. It is also important that the laser beambe angled, as shown in FIG. 1, consistent with the local directionallines of hair growth to provide recipient sites, each of which areslit-shaped and formed in the alopecic tissue.

Higher repetition rates produce a greater hemostatic effect, althoughthe required degree of hemostasis for hair transplantation is minimal.Simple clinical experiments performed by the author (unpublished)indicate that presence of blood does not significantly affect clinicaloutcome under the regime described above, although operator pathogenexposure risk increases. Concurrent use of smoke evacuation, aspracticed with superpulsed CO₂ lasers, minimizes interference and safetyrisk from particulate debris.

From the foregoing it has become apparent that a laser source emittingin the wavelength region 2.5-3.5 μm, with variable pulsewidth and spotsize capabilities, has potential for dermatological tissue ablation.This invention addresses the harnessing of these basic principles bymeans of appropriate apparatus and treatment method development toproduce optimal therapeutic results. In particular, it is believed thatthe subject matter of this invention will improve the precision ofablation and will meet the conditions required for the ablativepreparation of a recipient site for transplantation of hair bearingtissue grafts. It is important that the source be a laser, with itsattendant coherence, rather than an incoherent source such as, forinstance, a flashlamp-based source. Coherent light is unidirectional innature and better suited to precise targeting of human tissue.

Further, adverse sequelac associated with currently availabletechnologies will be reduced under the practice of this invention. Inparticular, a reduction in the extent of the proximal tissue coagulationand necrosis associated with use of the CO₂ laser is likely, leading toenhanced graft viability. In addition, the physical ablation and removalof alopecic scalp will allow for an ultimately higher density of hair onthe formerly alopecic section of scalp. A careful angling of theexposing laser beam will further allow graft tissue to be implanted in adirection consistent with that of local hair growth.

It is useful to consider prior reported use of the erbium laser toablate other body constituents, such as hard dental tissue. Hard dentaltissue such as enamel and denting present lower water content (2% and13% respectively) than skin tissue (approximately 70%), and accordinglyexhibit less favorable ablation when exposed to wavelengths which arehighly absorbed in water, such as those in the range 2.5-3.5 μm. As aconsequence, use of the erbium laser on dry hard dental tissue isassociated with poor ablation efficiency and wide lateral thermaldamage. Adjunctive use of a fine layer of water is described by Burkes(Burkes, E. J., et. aL, Jour. Pros. Dent., 1992, 67, 847-851), Hibst(Hibst. R., Keller, U.; SPIE vol. 2623, p.139-144) and Lukac (Lukac, M.,SPIE vol. 2080, pp. 51-54). Burkes notes that presence of a water filmof the appropriate thickness directly enhances ablation of enamel anddenting adjunctive to the expansion of the water vapor as it absorbsenergy. Hibst and Lukac comment that the water film may spare underlyingtissue by drawing heat away from the site, although Lukac notes a slightreduction in ablation rate, contrary to the findings of Burkes.

The author of this application is unaware of any reported use ofadjunctive water spray to assist the ablation process in dermatologicalapplications. Instead, water has been used to irrigate and clean debrisfrom the treatment site. In this invention, the apparatus is modified toinclude a fine water spray, which the author believes will improveablation efficiency and which will reduce lateral tissue damage, even inhigh water content dermatological tissue.

The above represents a summary of the theoretical considerationsemployed to calculate an appropriate parameter set, apparatus design andtreatment method. As part of this invention, an Erbium laser is used toeffect the optimal treatment method devised here. The laser handpiece isfurther characterized by an angled beam delivery, facilitated by anangled stand-off, and by an available elliptical spot shape, forimproved cosmesis. The handpiece also has gas and liquid entry ports.

General Treatment Procedures and Preferred Details:

The treatment site and patient are first medicated. Epinephrine(1:200,000) should be used to reduce bleeding during site preparation.Other medications may be applied over a longer period of time to modifythe healing response of the tissue and reduce incidence of adverseeffects.

An energy fluence in the range 1-200 J/cm² and pulsewidth in the range100-2000 microseconds, will typically be used. The recipient site may beprepared with a single circular or elliptical exposure spot with area inthe range 10⁻³ to 10⁻¹ cm², or with several spots constituting anelongated slit. Multiple pulses are applied to each site, until thephysician determines that an adequate crater depth has been realized.Coherent pulsed light with wavelength in the range 2.5-3.5 μm is used,with a wavelength of 2.94 μm being optimal. A concurrent water spray maybe applied.

Many such sites are prepared over the area of alopecic scalp. Adjacentsites (31) are linearly offset, as shown in FIG. 5.

Transplanted hair bearing tissue segments are then placed in thecraters. One preferred specification for the treatment device is listedbelow:

Host material: Er:YAG

Wavelength range: 2.94 μm

pulsewidth: 0.1-2.0 milliseconds

exposure fluence: 1-200 J/cm²

repetition rate: 1-20 Hz.

spot area on skin: 0.001-0.1 cm², variable

spot shape on skin: round, elliptical or rectangular

delivery system: fiber, with dermatology handpiece termination

handpiece: designed for angled or normal application of light

handpiece features: optional administration of inert gas and water

aiming beam: red diode or helium neon laser (1-10 mW)

This preferred embodiment can specifically be utilized for thepreparation of angled recipient sites for hair bearing excised scalptissue.

A second alternative embodiment employs the use of a different hostmaterial containing Erbium ions, such as Er:YSGG.

This first preferred embodiment is sketched as FIG. 3:

In practice, a separate footswitch (not shown) provides triggering tothe laser source found within the laser head cabinetry (11). The sourceincorporates a flashlamp-pumped rod containing active Erbium ions. Lightfrom this rod is directed along an articulated arm or fiber deliverysystem (12) to a handpiece containing focusing lenses (13). Theselenses, together with an available angled standoff distance gauge (14),provide precise positioning and focusing of the treatment beam (15) ontothe patient's skin (16). An inert `purging` gas is directed through thehandpiece from an inlet (17) to keep the treatment area and localfocusing lenses clear of debris. A fine water spray is introduced viaport (18), adjacent to the purging gas inlet. An incorporated visible`aiming beam`, within the cabinetry enclosure, also delivered throughthe light guide, provides verification of the ultimate placement of theinvisible treatment laser spot.

Further detail of one embodiment of the distal beam delivery apparatusis shown in FIG. 4. Here, the distal end of the articulated arm is shown(21), together with the internally propagating beam (22). A smalldiameter water flow tube (24) is shown, terminating in a fine nozzle(23). The beam is focused onto the tissue at a focal point (25).

Clinical Treatment Methodology

The goal of the treatment is to precisely prepare angled recipient siteswith minimal adjacent thermal coagulative damage. Below is presented anoptimal and novel therapeutic treatment methodology suitable for such aclinical application.

Dermatological Applications:

(i) Preparation of precise recipient sites for hair transplantation.

(ii) Precise dermatological tissue ablation.

A number of major advantages and conveniences are provided by thepresent treatment method, including:

1. The present methodology envisages the use of a specific parameter setchosen to provide optimum selectivity of damage to and ablation of thetarget tissue only. This precision results from the optimal absorptionof the Erbium wavelength and the limited conduction which results fromthe short microsecond domain pulsewidth. An optional water spray mayalso be introduced to enhance ablation precision and minimize lateraldamage. Minimal adjacent damage provides maximum opportunity forviability of the transplanted graft.

2. Alopecic scalp is actually removed, rather than pushed aside,resulting in an opportunity for maximum ultimate transplanted hairdensity in terms of ratio of hair bearing to alopecic scalp.

3. Angled application of narrow band coherent light provides forrecipient site orientation parallel to that of local hair growth, foroptimum cosmesis.

4. The procedure is relatively rapid and efficient and may be suitablefor future automation, in which an irregular grid structure could becreated by scanning the beam over an alopecic area.

General Treatment Procedures and Preferred Details:

The treatment method, according to one embodiment of the invention,includes:

irradiating a selected treatment site of alopecic scalp tissue with apulsed coherent light having a wavelength substantially in the range of2.5-3.5 μm, the light having an energy fluence substantially in therange of 1-200 J/Cm², a pulsewidth substantially in the range of100-2000 microseconds, and a spot area incident on the treatment sitesubstantially in the range of 10⁻³ to 10⁻¹ cm²,

controlling exposure duration at the treatment site of the light toproduce with the irradiation a controlled ablation depth of 1-5 mm atthe treatment site,

directing the light to produce a plurality of recipient sites in saidalopecic scalp tissue, whereby slit-shaped recipient sites are producedwhich are suitable for receiving transplanted grafts, wherein each ofthe slit-shaped sites is angled in a direction corresponding to a localprevalent direction of hair growth (FIG. 1), and

further directing the light to produce the recipient sites in anirregular grid pattern wherein the slits having adjacent positions arelinearly offset.

The treatment method is further characterized by:

Controlling hemostasis using intra-dermal epinephrine containing (1:200000) anesthesia.

Allowing the skin to heal for a period of 2-16 weeks.

Detailed Protocol

For a period of up to several weeks prior to treatment, the patient maybe premedicated with retinoic acid to speed healing, hydroquinone toreduce local pigmentary response, and/or a viral agent such asacyclovir.

The recipient scalp area to be treated is photographed under controlledconditions. It is further examined to detect the presence of scarring orotherwise abnormal color or texture.

Individual sites are designated and marked on the scalp. Each site isthen exposed with a chosen parameter set under optional irrigation. Atypical parameter set would be: 1000 mJ energy, 1 mm circular spot size(approximately 127 J/cm²), 15 Hz repetition rate, wavelength 2.94 μm,pulsewidth 300 μsec. Another typical parameter set would be: 600 mJ ofenergy, 0.75 mm spot size (approximately 140 J/cm²), 10 Hz repetitionrate, wavelength 2.94 μm, pulsewidth 300 μsec. Exposure would beeffected for 1-2 seconds, resulting in a crater of depth approximatelyequal to 1-5 mm. Several such adjacent spots would be placed resultingin a single slit-shaped recipient site of approximate size 1×3 mm.

The resultant site will be inspected to ensure that a clean crater edgehas been produced, with little evident charring. Charring is indicativeof local thermal damage and may be reduced as appropriate in adjacentsites by reducing the applied fluence or by reducing the repetitionrate.

Following treatment, a topical antibiotic and/or antiviral ointment maybe applied to the treated site and the skin area covered with adressing.

The patient will return several times after treatment for evaluation andassessment of graft viability. These visits will typically occur atintervals of 3 days, 1 week and thereafter monthly.

We claim:
 1. A laser treatment method for the preparation of pluralrecipient sites for implanting hair-bearing tissue on skin of a human,said method comprising the successive steps ofpremedicating a selectedtreatment site of a patient with a medicament; irradiating said selectedtreatment site of alopecic scalp tissue with erbium pulsed coherentlight having a wavelength substantially in the range of 2.5-3.5 μm, saidlight having an energy fluence substantially in a range of 1-200 J/cm²,a pulsewidth substantially in a range of 100-2000 microseconds, at anon-orthogonal angle incident to said treatment site and a spot areaincident on said treatment site substantially in a range of 10⁻³ to 10⁻¹cm² ; controlling exposure duration at said treatment site to produce acontrolled ablation depth of 1-5 mm at said treatment site; directingsaid light with a distance gauge for non-orthogonal administration ofenergy to produce a plurality of recipient sites in said alopecic scalptissue, whereby slit-shaped recipient sites are produced which aresuitable for receiving transplanted grafts, wherein each of saidslit-shaped sites is angled in a direction corresponding to a localprevalent direction of hair growth; and further directing said light toproduce said recipient sites in an irregular grid pattern wherein saidslits have adjacent positions which are linearly offset.
 2. The methodaccording to claim 1, further comprising the step of irrigating saidtreatment site with a cooling fluid concurrently with said irradiatingstep.
 3. The method according to claim 2, further comprising the step ofintroducing a flow of inert gas directed at a handpiece connected to asource of said light to reduce collection of debris on said source. 4.The method according to claim 1, wherein said medicament speeds healingabout said treated site.
 5. The method according to claim 4, whereinsaid medicament is retonoic acid.
 6. The method according to claim 1,wherein said medicament reduces local pigmentary response about saidtreated site.
 7. The method according to claim 6, wherein saidmedicament is hydroquinone.
 8. The method according to claim 1, whereinsaid medicament is an antiviral agent.
 9. The method according to claim8, wherein said medicament is acyclovir.
 10. The method according toclaim 1, wherein said medicament reduces bleeding about said treatedsite.
 11. A laser treatment method for ablation of human skin, saidmethod comprising the successive steps ofpremedicating a selectedtreatment site of a patient with a medicament; irradiating said selectedtreatment site of alopecic scalp tissue with erbium pulsed coherentlight having a wavelength substantially in the range of 2.5-3.5 μm, saidlight having an energy fluence substantially in a range of 1-200 J/cm²,a pulsewidth substantially in a range of 100-2000 microseconds, with adistance gauge for administration of energy at a non-orthogonal angleincident to said treatment site and a spot area incident on saidtreatment site substantially in a range of 10⁻³ to 10⁻¹ cm² ; andirrigating said treatment site with a cooling fluid concurrently withsaid irradiating step.
 12. The method according to claim 11, furthercomprising the step of introducing a flow of inert gas directed at ahandpiece connected to a source of said light to reduce collection ofdebris on said source.
 13. The method according to claim 11, whereinsaid medicament speeds healing about said treated site.
 14. The methodaccording to claim 13, wherein said medicament is retonoic acid.
 15. Themethod according to claim 11, wherein said medicament reduces localpigmentary response about said treated site.
 16. The method according toclaim 15, wherein said medicament is hydroquinone.
 17. The methodaccording to claim 11, wherein said medicament is an antiviral agent.18. The method according to claim 17, wherein said medicament isacyclovir.
 19. The method according to claim 11, wherein said medicamentreduces bleeding about said treated site.
 20. The method according toclaim 11, further comprising the step of irrigating said treatment sitewith a water spray to enhance ablation precision, concurrently with saidirradiating step.
 21. The method according to claim 11, wherein saidcooling fluid is a spray.
 22. The method according to claim 21, whereinsaid cooling fluid is water.
 23. A therapeutic treatment device forablation of skin tissue comprisinga laser head having a controllablelaser and a cooling unit for providing a cooling fluid at a dermaltreatment site of irradiation by said laser an articulated deliverysystem connected to said laser head terminated in a handpiece containinga focusing optics element and a distance gauge.